[CentOS] Setting read/write file access on cifs mounted file system

I'm accessing a cifs mounted file system (on a MS Windows XP machine)
from my CentOS 5 box. I can't edit/save files on the remote cifs system
using OpenOffice etc, although I can copy/paste whole files OK (ie from
CentOS to cifs). I've looked at the permissions on the mounted cifs and
see that I have folder access "create and delete files" but not file
access (the setting is blank). I've tried setting file access (as root)
to read and write, but it doesn't allow me to do this - any suggestions
as to how to resolve this please?

Thanks,
Andy